Woofer excursion

[Roy_L]

Over the years, especially with 2way speakers, I came to appreciate long excursion (travel distance) mid-woofers.
There are speakers which seem to be capable of high dynamic range, while others of the same size just bottom out under pressure. (For example, in playing Pink Floyd's song "Hey You" loudly, when the drums kick in at 1:18. Some speakers can take it easily, while others could be seriously damaged).
Is there a trade-off here? Or are long excursion drivers just better? Also, is this something detailed under a driver's specs?

 

[mhardy6647]

Well, there's Doppler distortion, much reviled by Col. Paul Klipsch.

 

[sergeauckland]

One difficulty with long-throw drivers is maintaining linearity over a long magnetic gap. There are two main methods, having a long coil in a short magnetic gap, which means that there's always the same amount of coil in the gap over the excursion, or having a short coil in a long magnetic gap, which accomplishes the same thing. The difference is in the size and shape of the magnet, and the resulting cost, and the reduction in sensitivity, as in both cases, either a lot of the coil or the magnet is 'wasted', leading to low sensitivity. However this gives good linearity and I'm always a bit suspicious of small high-sensitivity drivers as they will inevitably be compromised in LF distortion due to limited extension.

Large loudspeakers don't need much excursion to shift air, so are less limited in sensitivity and distortion, but of course are larger and more costly, and result in bigger boxes which may limit their commercial appeal.

As I'm not that bothered about enclosure size, I prefer a big driver in a big box, but then big drivers need crossing over fairly low, so need three or four ways, so more complexity and expense.

Isn't loudspeaker design just balancing compromises?

S.

 

[mhardy6647]

"We" have recently invoked what's known as Hofmann's Iron Law in a couple of recent threads. Here's an opportunity to invoke it yet again, in the context of the comments above by @sergeauckland

I (again) paraphrase glibly:

* Small Enclosure Volume
* (Deep) Bass Extension
* High Sensitivity
Pick two.

see, e.g., https://klhaudio.com/wp-content/upl...er-design-hofmans-iron-law-by-henry-kloss.pdf

A (partial) corollary, much beloved in certain... esoteric... hifi circles: There's no replacement for displacement.

 

[voodooless]

Also, is this something detailed under a driver's specs?

Yes, it’s called Xmax. Sadly it isn’t exactly a standardized number. Some define it as the 10%THD point, others use some magic formula.